We took a look at these drivers and found that the first link seemed to
be a really clean implementation of the virtio infrastructure and
virtio-net driver. We decided to stop the porting effort of the
NetBSD-based virtio drivers and instead use the FreeBSD ones. We
successfully ported the FreeBSD virtio infrastructure and virtio-net
driver, which now works and is ready for more testers.

In order to port this driver, we had to make some changes to the kernel:
essentially add kern/subr_sglist.c from FreeBSD and make a probe
interface public. The patch file is in the top-level directory of the
git tree and was diff'd from master this morning. The file name is:
0001-kern-changes-for-freeebsd-virtio-driver-port.patch

Regarding the original virtio-blk driver we ported from NetBSD. I will
probably port this to the new virtio-infrastructure, unless the FreeBSD
virtio-blk driver is posted on the FreeBSD mailing list in the near future.